1. Field of the Invention
The present invention relates to an ink jet printer which discharges an ink onto a recording medium thereby recording information on the recording medium.
2. Related Background Art
In general, presence of voids or air bubbles in the ink within orifices of ink jet head of an ink jet printer deteriorates the image reproducibility of the printer by allowing white blanks to be formed in the printed characters. In order to eliminate this problem, ink jet printers are usually provided with a suction recovery system which induces air stagnant in the orifices.
The suction recovery system includes a vacuum pump which sucks, through a cap, air from each nozzle which is designed to discharge droplets of the ink.
In order to improve the precision of operation of the suction recovery system, the present applicant has proposed an improved system in which a valve mechanism is provided in the suction passage between the vacuum pump and the cap, as in Japanese Patent Application No. 159057/1985.
The viscosity of the ink used in ink jet printers changes in accordance with the temperature. More specifically, the ink exhibits a smaller viscosity and, hence, a higher fluidity, as the ink temperature rises. Conversely, a reduction in the ink temperature increases the viscosity of the ink with the result that the ink becomes less fluid.
In consequence, an operation of the suction recovery system for inducing air when the ink temperature is high tends to cause an excessively large quantity of ink to be induced together with the air, due to the reduced viscosity of the ink, even if a valve mechanism is provided in the suction passage.
Thus, from the economical point of view, the ink tends to be induced wastefully during operation of the recovery system.